Stain resistant nylon fibers

ABSTRACT

Nylon carpet fibers are provided which resist staining by acid dye colorants at room temperature, yet are dyeable at elevated temperatures with acid dyes without losing their resistance to acid dye colorants at room temperature. The fibers are characterized by having a coating on the surface thereof comprising one or more selected compounds (stain blockers). Carpets comprising the fibers resist staining when exposed for long periods of time to spills containing acid dye colorants. By also including a fluorochemical in the coating, the carpets can resist such staining even after being subjected to heavy human trafficking.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of copending application Ser. No.834,804, filed Mar. 6, 1986 and now abandoned. Application Ser. No.834,804 is a continuation-in-part of copending application Ser. No.643,606, filed Aug. 23, 1984, and now abandoned. Application Ser. No.643,606 is a continuation of application Ser. No. 562,370, filed Dec.16, 1983, and now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to nylon fibers having unusual and beneficialdyeing characteristics. More specifically, the invention relates tonylon fibers which resist staining by acid dyes at ambient temperaturesand yet are capable of being dyed at elevated temperatures with aciddyes without losing their resistance to staining by acid dyes at ambienttemperatures. Conventional nylon fibers can be permanently stained atroom temperature by acid dye colorants commonly found in householditems, such as beverages, foods, cosmetics, medicines, etc. The nylonfibers of the invention have the ability at room temperature to resiststaining normally caused by these colorants and therefore areparticularly suited for use in the construction of carpets.

The term fiber as used herein includes fibers of extreme or indefinitelength (i.e. filaments) and fibers of short length (i.e. staple). Theterm yarn, as used herein, means a continuous strand of fibers.

The terms "stain" and "staining" as used herein with reference to nylonfibers means discoloration of such fibers caused by the chemicalreaction thereof with a substance such as an acid dye.

2. Description of the Prior Art

Carpet made from nylon fibers is a popular floor covering for bothresidential and commercial applications. Such carpet is relativelyinexpensive and offers a desirable combination of qualities, such asdurability, asesthetics, comfort, safety, warmth and quietness. Also, itis available in a wide variety of attractive colors, patterns andtextures. However, nylon fibers are severely and permanently stained bycertain artificial and natural colorants present in common householditems, such as Kool Aid® from nylon fibers is vulnerable to the spillingof such items. The vast majority of these colorants are acid dyes, allof which have been approved by the Food, Drug and Cosmetic Commissionfor human consumption. One of the most commonly used acid dye colorantsand one which most severely stains nylon at room temperature is FD&C RedDye No. 40 (hereinafter referred to as "Red Dye No. 40"). Red Dye No. 40(also known as C.T. Food Red 17) has the following structure. ##STR1##

Nylon carpet fibers are often coated with a fluorochemical either beforeor after the carpet is made for the purpose of improving the antisoilingcharacteristics of the carpet surface. The fluorochemical reduces thetendency of soil to adhere to the fiber thereby making the removal ofsoil from the carpet much easier than if the fluorochemical were omittedand, although this fluorochemical treatment also reduces fiberwettability, it offers very little protection to the carpet from spillscontaining acid dye colorants unless such colorants are immediatelyremoved from the carpet within five to seven minutes. In contrast tosubstances such as lipstick, shoe polish and motor oil which are capableof being physically removed from nylon carpet by recognized cleaningprocedures, acid dye colorants, such as Red Dye No. 40, penetrate andchemically react with nylon to form bonds which make complete removal ofsuch colorants from the nylon fibers impossible; the fibers are actuallydyed by these colorants within minutes and, therefore, permanentlystained.

Surveys of the carpet replacement market show that more carpets arereplaced due to staining than due to wear. Therefore, there is a need inthe art to provide nylon carpet fibers from which a more stain-resistantcarpet can be made.

SUMMARY OF THE INVENTION

The present invention provides nylon fibers which resist staining byacid dye colorants at ambient temperatures and yet are capable of beingdyed at elevated temperatures with acid dyes in a conventional mannerwithout losing their resistance to the acid dye colorants at ambienttemperatures. The nylon fibers of the invention are characterized byhaving a coating on the surface thereof comprising one or more stainblockers in an amount sufficient to provide a fiber having a "dyeabsorption value", hereinafter defined, at 25° C. of no greater than 7%and at 100° C. of no less than 30%.

The term "stain blocker" as used herein means a chemical compound whichwhen applied to a nylon fiber as a coating in the amount of 0.35% orless, based on the weight of fiber, provides a fiber having a dyeabsorption value of no greater than 7% at 25° C. and no less than 30% at100° C.

The fibers of the invention are particularly useful for providing stainresistant nylon carpets. Such carpets can withstand exposure to massivespills of substances containing acid dye colorants, such as red winesand soft drinks, for long periods of time without staining.

According to a preferred embodiment of the invention the coating on thesurface of the fiber comprises, in addition to one or more stainblockers, one or more fluorochemicals in an amount sufficient to providefibers which, when used in the construction of carpet, provides carpetretaining a greater portion of its original stain resistance after beingsubjected to 30,000 traffics than corresponding carpet from which thefluorochemical is omitted. The term "traffic" as used herein means theoccurrence of an individual walking across the carpet. By "originalstain resistance" is meant the stain resistance of new carpet beforetrafficking or any other exposure thereof to wear has occurred. Thefluorochemcial by itself does not impart significant stain resistance tonylon fiber nor does the fluorochemical, when used in combination withthe stain blocker, provide better stain resistance initially (i.e.before trafficking) than does the stain blocker by itself. Surprisingly,however, the use of one or more fluorochemicals in combination with thestain blocker(s) improves the retention of the original stain resistanceimparted to the fiber by the stain blocker.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plot showing the effect of temperature on the dye absorptiontest values of nylon fiber of this invention and of conventional nylonfiber.

FIG. 2 is a plot showing the effects of stain blocker and fluorochemicalon the stain resistance of nylon fiber before and after trafficking.

FIGS. 3-6 are photographs. Each photograph is of a cut pile carpetsample taken from above. The tufts of each of the carpets were made fromnylon yarn. Each carpet was exposed to Red Dye No. 40 for periods of 1,2, 4, 6 and 8 hours. Each photograph was taken under identicalconditions and at a reduction of 2.67 times. The yarn in each carpet isidentical, except the fibers of the yarns used to make the carpets shownin FIGS. 3 and 5 were coated in accordance with this invention and theyarns (Control) used to make the carpet shown in FIGS. 4 and 6 were not.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Any nylon fiber may be coated in accordance with the present invention.Nylon fibers of commercial importance are those shaped from nylon 66(polyhexamethylene adipamide) and nylon 6 (polycaprolactam). Theinvention is particularly useful for providing nylon carpet yarns fromwhich stain resistant carpets can be made. The coating is preferablyapplied to the nylon fibers from a finish (spin finish) during the meltspinning process used to prepare the fibers. Appropriate amounts of thestain blocker and fluorochemical are incorporated into the finish whichtypically contains lubricating oils for the fibers as well asdispersants for such oils.

Stain blockers which are particularly useful in practicing theeinvention include, by way of example, polymeric condensation productsconsisting essentially of repeating units of the formula ##STR2## whereR is the same or different in each unit and is hydrogen or a radicalselected from the group consisting of --SO₃ X, ##STR3## where X ishydrogen or a cation such as sodium or potassium. These condensationproducts are commercially available and can be prepared by conventionalmethods in the laboratory. Preferred condensation products of thisstructure are the water soluble products in which at least 40% of therepeating units contain an --SO₃ X radical and at least 40% of therepeating units contain the ##STR4## linkage. The molecular weight ofthe condensation products should be as high as possible while retainingsome water solubility and should contain as many monosulfonated phenylradicals as possible. Such products are conveniently prepared by thecondensation of formaldehyde with one or more appropriate phenols (orderivative thereof) such as in an acid or alkaline medium at elevatedtemperatures. Typically, in an acid medium, from 0.3 to 0.5 moles offormaldehyde is used for each mole of phenol and, in a basic medium,from 0.9 to 1.5 moles of formaldehyde is used for each mole of phenol.The water solubility of the condensation product is influenced by thetype of terminal groups present in its structure, for example,hydrophylic groups such as --CH₂ OH and --CH₂ SO₃ H render the productmore water soluble than groups, such as methyl or phenyl groups. Thebasic condensation provides products having a greater proportion ofterminal --CH₂ OH groups and, therefore, greater water-solubility.

Polymeric condensation products consisting essentially of theabove-mentioned repeating units can also be prepared by the methodwherein diphenolsulfone, after acetylation of its hydroxyl groups, issulfonated, then hydrolyzed to convert the acetylated hydroxyl groupsback to free hydroxyl groups, and finally, reacted with formaldehydeunder alkaline or acid conditions. In this instance, reaction conditionsare selected to avoid or at least minimize the formation of productscontaining di-and/or trisulfonated phenyl groups. In general,condensation products in which each repeat unit contains only one --SO₃X radical are more effective stain blockers than corresponding productsin which each repeat unit contains two or more --SO₃ X radicals. Also,in general, as the ratio of units containing one --SO₃ X radical tounits containing no --SO₃ X radicals increases, the product becomes amore effective stain blocker.

Condensation products of Formula I are commercially available, forexample, mixed condensation products of phenol sulfonic acid withdihydroxy diphenolsulfone and formaldehyde are available from Ciba-GeigyCorp. under the tradename of Erional® PA or from Crompton and KnowlesCorp. under the tradename of Intratex® N.

Also, useful as stain blockers in practicing the present invention aremixed condensation products of naphthalene monosulfolnic acids withdihydroxy diphenylsulfones and formaldehyde. Such a product is soldcommercially by Ciba-Geigy Corp. under the tradename of Erional NW.

Fluorochemicals useful in practicing the present invention are thosewhich, when applied as a coating to nylon fiber in combination with astain blocker, wherein the fluorochemical and stain blocker are appliedin amounts sufficient to provide a coating comprising 0.35% by weight ofstain blocker and 650 ppm fluorine, based on the weight of fiber, andthe fiber is used in the construction of carpet, the carpet retains agreater portion of its original stain resistance after being subjectedto 30,000 traffics than if the fluorochemical were omitted from thecoating. Such fluorochemicals include, by way of example, thosecommercially available for use with fibers, such as those commerciallyavailable from Minnesota Mining and Manufacturing Company under thetradename of Scotchgard® (Scotchgard 358 and 352) and from E. I. DuPontde Nemours and Company under the tradenames of Zepel® and Teflon®.Typically, these fluorochemicals contain a perfluoroalkyl radical(R_(f)) having from 3 to 20 carbons and is the condensation product ofR_(f) OH or R_(f) NH₂ with a suitable anhydride or isocyanate, forexample, the reaction product of N-ethylperfluorooctyl-sulfonamideoethanol and toluene diisocyanate in a 2:1mole ratio.

Preferably, the coating on the nylon fiber of this invention comprisesfrom 0.20 to 0.35% by weight (2000 to 3500 ppm) of stain blocker(s),based on the weight of the nylon, and sufficient fluorochemical(s) toprovide from 450 to 650 ppm of fluorine, based on the weight of thenylon. The stain blocker(s) and fluorochemical(s) may be appliedseparately or simultaneously. According to a preferred embodiment of theinvention, the stain blocker(s) and fluorochemical(s) are appliedsimultaneously to the nylon fiber from a finish. According to thisembodiment, the stain blocker(s) and fluorochemical(s) are of the samecharge, that is, both anionic or cationic, so as to avoid anypossibility of precipitation thereof in the finish. The above-mentionedsulfonate-containing stain blockers are anionic and, therefore, it ispreferable when using these stain blockers to use anionicfluorochemicals. However, it is possible to select appropriatedispersants so as to form a suitably stable finish containing oppositelycharged components.

Selection of an optimum combination of stain blocker(s) andfluorochemical(s) for a particular application can be made from a widevariety of stain blockers and fluorochemicals and the fine tuning of theselection to provide optimum results with a given nylon fiber appliedunder a set of given conditions can be achieved by routineexperimentation within the capabilities of those skilled in the art bymerely testing various combinations of components and selecting thecombination giving the best results.

Typically, nylon carpet yarn ready for tufting is a two-ply staple orcontinuous filament yarn which has been subjected to a heat treatment toset the twist in the yarn. The treatment is referred to as heatsetting.Conventionally, the heatsetting operation is accomplished using eitherSuperba equipment in which case the yarn is subjected to steam at about130°-140° C. or Suessen equipment in which case the yarn is subjected tohot air at about 195°-205° C. The adhesion of the coating on the nylonfiber of this invention is enhanced by subjecting the coated fiber toSuessen heatsetting conditions. Maximum adhesion of the coating of thefiber is achieved when the coating comprises a stain blocker which hasterminal groups that can further react during heatsetting with itself orwith the nylon surface. Reaction of the terminal groups of the stainblocker with the nylon surface results is covalent linkages. Stainblockers having such groups include those prepared under alkalineconditions.

Preferably, the stain blocker(s) and fluorochemical(s) are selected andapplied to the nylon fibers so as to provide fibers having dyeabsorption test values of 4% or less and, most preferably, of zero orsubstantially zero (no visible stain) at temperatures up to andincluding 25° C. and, most preferably, at temperatures up to andincluding 50° C. and yet have dye absorption test values at 100° C. ofat least 30% and, most preferably, of at least 60%.

Dye absorption test values, when given herein, are given in terms of thepatent (%) of Red Dye No. 40 absorbed by a fiber sample from an aqueoussolution of the dye with reference to the temperature of the solution.The test is accomplished as follows:

(1) An aqueous solution of Red Dye No. 40 in which the concentration ofthe dye is 0.054 gms/liter is prepared. (This is the concentration ofRed Dye No. 40 in cherry Kool Aid when commercialy obtained packagedingredients are mixed with water according to instructions on thepackage.)

(2) The light absorption (optical density) of the solution is measuredon a Cary 15 Spectrophotometer or equivalent instrument using a 1/2 cmcell with the measurement being made at 495 millimicrons, the maximumabsorptivity for Red Dye No. 40. (Light absorption is a measure of thedye concentration of the solution.)

(3) The light absorption reading is recorded as T₀.

(4) Then, 0.25 grams of test fiber is placed into a container containing14.8 ml of the Red Dye No. 40 solution and the pH of the solution isadjusted to 3 by adding an appropriate amount of Universal Buffer.

(5) The container is then sealed (e.g., stoppered) and shaken for aperiod of three hours, for example, by means of a motorized shaker at aselected temperature, the temperature being thermostatically controlled.

(6) The fiber is then removed from the solution and the light absorptionof the solution is again measured as before.

(7) The reading this time is recorded at T₁. (If the fiber sample is notstain resistant, it will take up dye from the solution and the T₁ valuewill be less than the T₀ value; on the other hand, if the fiber sampleis stain resistant, it will not take up significant dye from thesolution and the T₁ value will be the same or substantially the same asthe T₀ value.)

(8) The "Dye Absorption Test Value" at the selected temperature isexpressed as a percentage of the T₀ value and is calculated as follows:##EQU1##

The following examples are given to further illustrate the invention.

EXAMPLE 1

In this example, nylon 66 fibers of the present invention were preparedand tested to demonstrate their resistance to staining.

A 300 filament, 60 denier per filament (dpf), nylon 66 yarn was preparedby extruding fiber-forming nylon 66 of commercial grade at a melttemperature of 282° C. downwardly through the orifices of a 300-holespinneret into a conventional melt spinning chimney, measuringapproximately 1.8 meters in length to form a corresponding number ofmolten streams. The chimney was adapted to receive a cross-flow ofcooling air ambient temperature at a velocity of 270 meters/min. Themolten streams solidified in the chimney to form filaments. Thefilaments were passed from the chimney through a conventional steamconditioning tube measuring about 1.8 meters in length where thefilaments were treated with steam. The filaments were passed from theconditioning tube over a conventional metered finish applicator where anaqueous finish containing a stain blocker and fluorochemical in amountssufficient to provide 3500 ppm of the stain blocker and 650 ppm offluorine, each based on the weight of fiber, was applied and thefilaments converged to form a yarn. The yarn was then passed over andaround a driven feed roll (450 meters/min.) and its associated seperatorroll with several wraps. The yarn was then collected on a bobbin under aslight tension to facilitate winding of the yarn onto the bobbin. Theyarn was then unwound from the bobbin and combined with 54 like yarns toform a tow having a total denier of about 1,000,000. The tow was drawnover rolls to provide nominal 18 dpf tow, crimped in a conventionalstuffer box and cut into 71/2 inch (19.05 cm) staple. The staple wascarded, drafted, spun on a conventional ring spinning frame to provide a31/2 cotton count singles yarn having about 4.5 tpi (177 tpm) of twistin the Z-direction. Two of these yarns were then piled with 4.0 tpi (157tpm) of twist in the S-direction. A portion of the piled yarn washeatset using normal Suessen heatsetting conditions at 200° C.

The stain blocker (stain blocker A) used in preparing the above heatsetand nonheatset yarns consisted essentially of repeating units of theformula ##STR5## where R is ##STR6## and R' is --SO₃ Na in at least 50%of the units and is hydrogen in the remaining units. The fluorochemicalused in preparing these yarns was a mixture of anonic fluorochemicalsbased on N-ethylperfluorooctyl-sulfonamideoethanol.

Dye absorption test values of a sample of the heatset yarn (Yarn E) andthe nonheatset yarn (Yarn D) were determined at the various temperaturesindicated in Table 1 below. (The heatset yarn is represented by Curve Eand the nonheatset yarn by Curve D in FIG. 1.) Both (Yarn E) and (YarnD) are considered to be yarns within the scope of this invention.

In another run, heatset and nonheatset yarns (Controls) were prepared inthe same manner as described above except in this instance the stainblocker and fluorochemical were omitted from the finish. Dye absorptiontest values of a sample of the nonheatset Control yarn (Yarn A) weredetermined and are given in Table I. (This yarn is representative byCurve A in FIG. 1.) A sample of the heatset Control yarn (Conventionalnylon carpet yarn) was treated according to the techings of U.S. Pat.No. 3,118,723 by immersing the sample in an aqueous bath containing 2%by weight of acetic acid and 0.5% by weight of Erinoal NW, then bringingthe bath to a boil over a period of twenty minutes, holding the bath atthe boil for an additional hour, removing the yarn from the bath andthen washing and drying the yarn. Dye absorption test values of thisyarn (Yarn B) were determined and are also given in Table I. (This yarnis represented by Curve B in FIG. 1.) This treatment of the yarnsimulates treatment of carpet where Erional NW is added to the dye bath,as a dye auxiliary (leveling agent or reserving agent), during beckdyeing of the carpet.

A second sample of the nonheatset Control yarn was also treated inaccordance with the teachings of U.S. Pat. No. 3,118,723 (Example 1thereof) in the manner just described. The treated sample was thenheatset by heating the sample in an atmosphere of air at 200° C. for aperiod of one minute and then cooled to ambient temperatures. DyeAbsorption Test Values of this treated/heatset yarn (Yarn C) weredetermined and are also given in Table I below. (This yarn isrepresented by Curve C in FIG. 1.) Yarn C is considered to be a yarnwithin the scope of this invention. The treatment of this sample differsfrom the above treatment (prior art) in that in this instance the samplewas treated and then heatset, whereas in the above instance the samplewas heatset and then treated.

                  TABLE I                                                         ______________________________________                                        DYE-                                                                          BATH    DYE ABSORPTION VALUES (%)                                             TEMP.   INVENTION          Control  Prior Art                                 C.      YARN C   YARN D   YARN E YARN A YARN B                                ______________________________________                                        25      6.4      0.0      0.0    75.3   18.1                                  30      9.6      1.6      0.0    100.0  30.9                                  35      14.1     1.6      0.0    --     54.3                                  40      20.2     4.3      0.0    --     79.5                                  45      31.9     6.6      1.6    --     93.1                                  50      53.2     10.1     2.7    --     100.0                                 55      76.1     14.9     3.2    --     --                                    60      86.2     16.2     3.7    --     --                                    65      90.4     17.6     4.3    --     --                                    70      95.7     20.7     4.3    --     --                                    75      99.2     23.9     4.8    --     --                                    80      100.0    31.4     6.1    --     --                                    85      --       37.8     11.7   --     --                                    90      --       52.1     18.6   --     --                                    95      --       59.0     29.8   --     --                                    100     100.0    67.0     34.6   100.0  100.0                                 ______________________________________                                    

FIG. 1 is a plot of the data given in Table I. In FIG. 1 Curves A, B andC each terminate at the point defined by the intersection coordinates100° C. and 100%.

The data shown in Table I and represented in FIG. 1 dramaticallydemonstrate the exceptional stain resistant properties of the nylonfiber of the present invention as compared to prior art nylon fibers.With reference to FIG. 1, the fibers represented by Curves A and B eachwere stained at 25° C. to a bright red color and therefore lackedmeaningful stain resistance characteristics. The fiber represented byCurve C (Invention) was stained at 25° C. to a lighter shade of pinkand, while only marginally acceptable for some carpet yarn applications,was nevertheless significantly more stain resistant than the fibersrepresented by Curves A and B. Remarkably, the fibers represented byCurves D and E were not stained at all at 25° C.

EXAMPLE 2

This example illustrates the unexpected advantage gained by coatingnylon fibers with a fluorochemical and stain blocker. The example showsthat carpet made from these fibers retains a greater portion of itsoriginal stain resistance after trafficking than corresponding carpetmade from nylon fibers coated with only stain blocker.

Thirteen (13) 68 filament, 60 denier per filament (dpf), nylon 66 yarnswere prepared. Each yarn was prepared by extruding fiber-forming nylon66 of commercial grade at a melt temperature of 274° C. downwardlythrough the orifices of a 68-hole spinneret into a conventional meltspinning chimney, measuring approximately 1.8 meters in length to form acorresponding number of molten streams. The chimney was adapted toreceive a cross-flow of cooling air at 18.3° C. at a flow rate of 11.2m³ /min. The molten streams solidified in the chimney to form filaments.The filaments were passed from the chimney through a conventional steamconditioning tube measuring about 1.8 meters in length where thefilaments were treated with steam. The filaments were passed from theconditioning tube over a conventional metered finish applicator where anaqueous finish containing a stain blocker and/or a fluorochemical wereapplied. The stain blocker used in this instance was Erinol PA and thefluorochemical in this instance was Scotchgard FC 358. The level ofstain blocker and fluorochemical was varied from yarn to yarn as shownin Table II. Two of these yarns were plied as described in Example andthen draw-textured through a texturing machine to yield fibers of about18 dpf. The resulting two ply yarns were heatset in a Seussen heatsetting unit (200° C. for 1 minute). The yarns were used to provide twosets of identical samples each of which contained 13 strips with eachstrip being tufted with a different yarn. The resulting 26 strips wereblank dyed at a 40:1 liquor-to-goods weight ratio using a solution of2.5 wt. % Calgon on weight of goods (owg), 1.0 wt. % Alkanol ND owg and2.0 wt. % ammonium sulfate owg. The solution with the strips was thenheated to boiling over a 55 minute period and held at the boil withagitation for an additional 60 minutes. The liquor was removed. Thestrips were then rinsed three times with water, rung through rollerswith each rinse to a water pickup of 200% and, finally, allowed to dry48 hours under ambient conditions.

One set of the blank dyed strips was tested determine the original stainresistance of the different strips. The test consisted of applying 3drops of an aqueous solution of Red Dye No. 40 at a concentration of0.054 gms/liter to the surface of each strip (0.054 gms/lt is theconcentration of Red Dye No. 40 in cherry Kool Aid which was thesolution employed). The solution was worked into the strips by applyingpressure with a spatula. A red spot was formed on each strip. (Ten totwenty strokes of the spatula are usually sufficient to assurepentration of the solution into the fibers.) Each strip was then treatedin the following manner. Seven more drops of the solution was applied tothe spot, worked in with the spatula and left for a period of 10minutes. At the end of the 10 minute period, the spot was blotted withabsorbent paper towels until no further solution could be removed byblotting. The spot was then allowed to dry for 16 hours. Each strip wasthen cleaned by the following procedure. Four (4) ml. of a carpetcleaning solution was applied to the spot. The cleaning solution hadpreviously been made up by adding 28.4 grams of Steam Clean 300 PG (acommercially available product from Procter and Gamble Co.) to 473 mls.of deionized water. The cleaning solution was left on the spot for 30seconds and then blotted dry with absorbent paper towels. Then, 4 ml ofvinegar (5% acetic acid in deionized water) was applied to the spot andleft in contact with the spot for 30 seconds. After the 30 secondperiod, the spot was blotted dry. Then, 4 ml of the carpet cleaner wasapplied to the spot left for 30 seconds and then blotted dry. Finally,10 ml of deionized water was applied to the spot and the spot blotteduntil dry. The strips were then compared to six strips which had beenpreviously staned with Red Dye No. 40 to different degrees of stainingranging from no stain (1) to completely stained (6) where the differencein color between adjacent degrees of staining was substantially thesame. The strips were mounted on a board and the test strips werematched to a strip on the board and assigned its number. For numbersless than two, decimal grading is used to denote proximity between 1 and2. Strips which were assigned a grade of 2 or more were judged not tohave significant stain resistance and, therefore, failed the test.

Selected strips of the second set were floor tested for 30,000 trafficsand then subjected to the above stain resistance test to determine whateffect, if any, trafficking (wear) had on the original stain resistanceof the strips. The results of the testing before and after traffickingare given in Table II.

                  TABLE II                                                        ______________________________________                                                           Stain Testing Grade                                        Yarn  Stain blocker                                                                            Fluorochemical                                                                            Before  After                                    Sample                                                                              wt. %      ppm F       Trafficking                                                                           Trafficking                              ______________________________________                                        2A1   0.08       --          5(failed)                                                                             not tested                               2A2   --         200         4(failed)                                                                             not tested                               2A3   0.08       200         3(failed)                                                                             4                                        2B1   0.16       --          4(failed)                                                                             not tested                               2B2   --         400         2(failed)                                                                             not tested                               2B3   0.16       400         1.2     3                                        2C1   0.24       --          1.8     4                                        2C2   --         600         1.5     4                                        2C3   0.24       600         1.1     2                                        2D1   0.32       --          1.2     4                                        2D2   --         800         1.4     4                                        2D3   0.32       800         1.0     1.6                                      Con-  --         --          6(failed)                                                                             not tested                               trol                                                                          ______________________________________                                    

FIG. 2 is a plot of the data given in Table II. In FIG. 2 stain gradingnumbers not enclosed by parentheses are determined before trafficking(*)and those enclosed by parentheses are determined after trafficking(**).

The results given in Table II and shown in FIG. 2 clearly show that thenylon fibers coated with stain blocker and fluorochemical (e.g. 2D3)retained a greater portion of their original resistance aftertrafficking than corresponding fibers from which the fluorochemical wasomitted (2D1). The results also show the effect of stain blocker andfluorochemical concentrations on stain resistance.

EXAMPLE 3

In this example nylon fibers were coated with fluorochemical or stainblocker or a combination thereof and then tested for stain resistance.

Plied yarns were prepared as described in Example 1, except in oneinstance the finish contained neither stain blocker A nor fluorochemical(Control Yarn); in another instance the finish contained stain blocker Aand no fluorochemical (S.B. Yarn); in yet another instance the finishcontained fluorochemical and no stain blocker (F.C. Yarn); and in stillanother instance the finish contained both stain blocker A andfluorochemical (S.B.+F.C. Yarn). The fluorochemical used in thisinstance was the same as that used to prepare the yarn described inExample 1.

The stain blocker and fluorochemical, when present in the finish, werepresent in amount sufficient to provide 3500 ppm of the stain blockerand 650 ppm of fluorine on the yarn, based on the weight of yarn. Allthe yarns were heatset at 200° C. using normal Suessen heatsettingconditions. Dye absorption test values of a sample of each yarn weredetermined at 30° C. and at 100° C. and are given in the followingTable.

                  TABLE III                                                       ______________________________________                                                   Dye Absorption Test Values, (%)                                    Yarn         30°  100°                                          ______________________________________                                        Control      85          100                                                  S.B.          5           68                                                  S.B. + F.C.   5           63                                                  F.C.         73          100                                                  ______________________________________                                    

The results in Table II show that the fluorochemical by itself did notimpart significant stain resistance to nylon fiber. The results furthershow that the fluorochemical when used in combination with the stainblocker did not improve the stain resistance of the stain blocker,thereby confirming the results given in Example 2 that the value of thecombinations is in retaining original stain resistance aftertrafficking, i.e., durability of stain resistance.

EXAMPLE 4

Two 31/2 cotton singles yarns were prepared as described in Example 1except that in this instance the stain blocker was Intratex N and theyarns were not individually heatset. A fluorochemical was not used. Theyarns were plied on a conventional ring twister with 3 tpi (118 tpm) oftwist in the S-direction. The resulting plied yarn was then heatsetusing Suessen heatsetting conditions at 200° C. Cut pile tufted carpetsamples were made from the heatset plied staple yarn and dyed to a lightgold color. Light gold was selected as being a color which contrastswell with most stains.

The carpet samples were subjected to the common household liquidsubstances in the table below to determine the resistance of the sampleto staining by colorants present in these substances. Each substance wasapplied to the carpet sample, rubbed into the carpet, left on the sampleovernight and, finally, the next day the sample was washed to remove thesubstance, first with a dilute water solution of a commercial detergentand then with water. For purposes of comparison, carpet samples(control) were made in the same manner described above except in thisinstance the yarns from which the samples were made were not treatedwith Intratex N, that is, Intratex N was omitted from the finish.

                  TABLE IV                                                        ______________________________________                                        Staining Results                                                                                 Carpet Samples                                             Substance            Invention Control                                        ______________________________________                                        Coffee/Cream/Sugar   Removed   Stained                                        Red Wine             Removed   Stained                                        Soft Drink w/Red Dye No. 40*                                                                       Removed   Stained                                        Cola                 Removed   Removed                                        Watercolor           Removed   Removed                                        Mustard w/out Tumeric                                                                              Removed   Removed                                        Mustard w/Tumeric    Stained   Stained                                        ______________________________________                                         *a soft drink was prepared by dissolving cherry Kool Aid premix               ingredients in the recommended amount of water.                          

The results in the Table clearly show that the nylon fibers treated inaccordance with the present invention had excellent stain resistance,whereas corresponding fibers which were not so treated lack stainresistance.

It was observed that the exposed cut ends of the pile fibers of thecarpet samples prepared from fibers of the invention were stainresistance, thereby demonstrating that the stain blocker not only coatedthe surface of the fibers but also impregnated the fibers.

EXAMPLE 5

Of the staining substances tested in Example 4, the substance which mostseverly stained the untreated (control) carpet samples was the softdrink (cherry Kool Aid) containing Red Dye No. 40. A separate test wasthen conducted to determine the effect of a massive spill of this softdrink on a carpet sample made from nylon 66 fibers of the presentinvention. In this test, a gallon (385 ml) of the soft drink was pouredonto an appropriate carpet sample from a gallon milk container thecontainer being held at a height of one meter above the face of thecarpet sample. The concentration of the dye in the soft drink was 0.054gms/liter. The carpet sample was made in the manner described in Example2, except half of the sample was made from yarn, the fibers of whichwere treated with Intratex N, and the other half (control) fromcorresponding yarn, the fibers which were not treated with Intratex N.The soft drink was poured onto both halves of the carpet sample from adistance of about one meter above the carpet sample with an attemptbeing made to pour the same amount on each half. The soft drink was lefton the sample overnight with no steps being taken to clean the carpet orremove any of the soft drink until the next day. The next day the carpetsample was cleaned in the manner described above. Surprisingly, afterbeing cleaned, no visible evidence of the soft drink (Red Dye No. 40)remained on that half of the carpet sample prepared from fibers of thepresent invention, whereas the other half of the carpet sample was badlystained.

Similar results were obtained when the stain blockers used in Examples Iand II were substituted for the stain blocker used in this example.

EXAMPLE 6

In this example, two nylon carpet yarns were prepared, one in accordancewith the present invention (stain-blocked yarn) and one in accordancewith state-of-the-art techniques (control yarn). The yarns were thenprocessed identically and each made into a cut pile carpet with bothcarpets being the same except one was made using stain blocked yarn andthe other was made using control yarns. The carpets were then tested forstain resistance before and again after trafficking.

The yarn of the present invention (stain-blocked yarn) was made in thefollowing way.

A 300 filament, 60 denier filament (dpf), nylon 66 yarn was prepared byextruding fiber-forming nylon 66 of commercial grade at a melttemperature of 282° C. downwardly through the orifices of a 300-holespinneret into a conventional melt spinning chimney, measuringapproximately 1.8 meters in length, to form a corresponding number ofmolten streams. The chimney was adapted to receive a cross-flow ofcooling air at ambient temperature at a velocity of 270 meters/min. Themolten streams solidified in the chimney to form filaments. Thefilaments were passed from the chimney through a conventional steamconditioning tube measuring about 1.2 meters in length where thefilaments were treated with steam. The filaments were passed from theconditioning tube over a conventional metered finish applicator where anaqueous finish containing a stain blocker and fluorochemical in amountssufficient to provide 3500 ppm of the stain blocker and 650 ppm offluorine, each based on the weight of fiber, was applied and thefilaments converged to form a yarn. The yarn was then passed over andaround a driven feed roll (450 meters/min.) and its associated separatorroll with several wraps. The yarn was then collected on a bobbin under aslight tension to facilitate winding of the yarn onto a bobbin. The yarnwas then unwound from the bobbin and combined with 54 like yarns to forma tow having a total denier of about 1,000,000. The tow was drawn overrolls to provide nominal 18 dpf tow, crimped in a conventional stufferbox and cut into 71/2 inch (19.05 cm) staple. The staple was carded,drafted, and spun on a conventional ring spinning frame to provide a31/2 cotton count singles yarns having about 4.5 tpi (177 tpm) of twistin the Z-direction. Two of these yarns were then plied with 4.0 tpi (157tpm) of twist in the S-direction. The stain blocker and fluorochemicalused in preparing this yarn were the same as those used to prepare theyarns described in Example 1.

The Control yarn was made in the same manner just described, except thatthe stain blocker and fluorochemical were omitted from the finish.

Both yarns were heatset using normal sluessen heatsetting conditions at200° C. A carpet of saxony construction was made from each yarn. Eachyarn was tufted on a 5/32 gauge cut pile tufting machine into a primarybacking using 7 stitches per inch (27.6 stitches per 10 cm). The pileheight was 7/8 in (2.2. cm) and 32 oz of yarn were used per square yardof carpet. Each carpet was dyed in a beck to a light beige shade ofcolor. A secondary backing was applied with an adhesive to the primarybacking. Each carpet was subjected to the following tests.

A sample of each carpet was tested to determine its resistance to RedDye No 40 before trafficking. An aqueous solution of the dye at aconcentrate of 0.054 gms/lt. (cherry Kool Aid) was prepared as describedin Example 4 and used in the testing of the carpet samples. Fiveopen-ended cylinders having an inside diameter of 2.54 cm and measuring10 cm in length were placed vertically on each carpet sample. Twenty(20) ml of the Red Dye No. 40 solution was poured into each of thecylinders at the time intervals shown below:

cylinder 1 at t_(o) (beginning)

cylinder 2 at t_(o) +2 hours

cylinder 3 at t_(o) +4 hours

cylinder 4 at t_(o) +6 hours

cylinder 5 at t_(o) +7 hours

At the end of eight hours (t_(o) +8), all the cylinders were removedfrom the carpet samples and the spots were blotted with paper towel toremove excess solution. The spots on each carpet sample were then gradedon a scale of 1 to 8 with 1 being severely stained carpet and 8 being novisible stain on the carpet. Each carpet sample was in contact with theRed Dye No. 40 solution for periods of 1, 2, 4, 6 and 8 hours. Each timeperiod solution corresponded to one of the spots on the carpet sample.The results of the testing is given in Table V.

                  TABLE V                                                         ______________________________________                                                 Before Trafficking                                                            Stain Testing Grade on a Scale of 1 to 8*                            Spot       Invention     Control                                              ______________________________________                                        1 hour     8.0           3.0                                                  2 hours    8.0           2.5                                                  4 hours    8.0           2.0                                                  6 hours    8.0           1.0                                                  8 hours    8.0           1.0                                                  Average    8.0           1.9                                                  ______________________________________                                         *1 designates severely stained                                                8 designates no visible stain                                            

A second sample of each carpet was subjected to 128,000 traffickings andthen tested in the manner just described. The results of this test isgiven in Table VI.

                  TABLE VI                                                        ______________________________________                                                 After 128K Traffics                                                           Stain Testing Grade on a Scale of 1 to 8*                            Spot       Invention     Control                                              ______________________________________                                        1 hour     8.0           3.0                                                  2 hours    7.0           2.0                                                  4 hours    6.0           1.0                                                  6 hours    5.0           1.0                                                  8 hours    5.0           1.0                                                  Average    6.2           1.6                                                  ______________________________________                                         *1 designates severely stained                                                8 designates no visible stain                                            

FIG. 3 is a photograph of the carpet made from the stain blocked yarn(Invention) before trafficking and after being subjected to the stainingtest. FIG. 4 is a photograph of the carpet made from the Control yarnbefore trafficking and after being subjected to the staining test. FIG.5 is a photograph of the carpet made from the stain blocked yarn(Invention) after being first subjected to 128,000 traffickings and thento the staining test. FIG. 6 is a photograph of the Control yarn afterbeing subjected first to 128,000 traffickings and then to the stainingtest.

The results given in Tables V and VI and shown in FIGS. 3-6 clearlyillustrate the unusual and beneficial stain resistant characteristics ofthe fiber of the invention. In FIGS. 3 and 4 the expression "original"means before trafficking and in FIGS. 5 and 6 the expression "soiled"means after trafficking. The results show that the fibers coated inaccordance with the invention were substantially stain proof withrespect to Red Dye No. 40, even after enduring 128,000 traffics, whereaswhen the coating was omitted from the fibers, the fibers virtually hadno protection from the dye. It is remarkable that the carpet made fromthe fibers of the invention was not stained at all before traffickingand stained very little after trafficking even though the dye was leftin contact with the carpet for periods of up to eight hours. Thiscorresponds, for example, to a small child spilling a soft drink and thespill going unnoticed for an extended period of time. Such an incidentis not uncommon in the typical household.

I claim:
 1. An undyed stained resistant nylon fiber characterized by having a coating on the surface thereof comprising one or more stain blockers in an amount sufficient to provide a fiber having a dye absorption test value at 25° C. of .[.no greater than 7%.]. .Iadd.substantially zero .Iaddend.and a dye absorption value at 100° C. of no less than 30%.
 2. The fiber of claim 1 wherein the nylon is nylon
 66. 3. The fiber of claim 1 wherein the denier of said fiber is in the range of 8 to
 24. 4. The fiber of claim 3 in staple form.
 5. The fiber of claim 3 in continuous filament form.
 6. A yarn composed of the fibers of claim
 4. 7. A yarn composed of the fibers of claim
 5. .[.8. The fiber of claim 1 wherein said dye absorption value at 25° C. is substantially zero..].
 9. The fiber of claim 1 wherein said coating also comprises one or more fluorochemical(s) in an amount sufficient to provide fiber having the ability when made into carpet of retaining a greater portion of its original stain resistance after trafficking than if the fluorochemical were omitted from the coating.
 10. The fiber of claim 1 wherein said stain blockers are polymeric condensation products consisting essentially of repeating units of the formula ##STR7## where R is the same or different in each unit and is hydrogen or a radical selected from the group consisting of --SO₃ X, ##STR8## where X is hydrogen or a cation, wherein at least 40% of said repeating units contain an --SO₃ X radical and at least 40% of the repeating units contain the ##STR9## linkage.
 11. The fiber of claim 10 wherein said condensation products are mixed condensation products of phenol sulfonic acid with dihydroxy diphenolsulfone and formaldehyde.
 12. The fiber of claim 1 wherein said stain blockers are mixed condensation products of naphthalene monosulfonic acids with dihydroxy diphenylsulfones and formaldehyde.
 13. A carpet having a pile consisting essentially of fibers of claim
 1. 14. The carpet of claim 13 wherein the carpet is of a cut pile construction.
 15. The carpet of claim 14 wherein the fibers are nylon 66 fibers.
 16. An undyed nylon fiber characterized by having a coating on the surface thereof comprising one or more stain blockers in an amount sufficient to provide a fiber having dye absorption test values within the range represented by the area under Curve C and above Curve E in FIG.
 1. 17. A carpet having a pile consisting essentially of fibers of claim
 16. 18. The carpet of claim 17 wherein the fibers are nylon 66 fibers.
 19. An undyed nylon fiber characterized by having a coating on the surface thereof comprising one or more stain blockers in an amount sufficient to provide a fiber having dye absorption test values within the range represented by the area under Curve D and above Curve E in FIG.
 1. 20. A carpet having a pile consisting essentially of fibers of claim
 19. 21. The carpet of claim 20 wherein the fibers are nylon 66 fibers.
 22. A process for improving the ability of nylon fibers to resist staining at room temperature by acid dyes while retaining their ability to be dyed with acid dyes at elevated temperatures which comprises applying a spin finish to said fibers during the melt polymerization process by which said fibers are prepared, said finish being characterized in containing one or more stain blocker(s) in an amount sufficient to provide a nylon fiber having a dye absorption value at 25° C. of .[.no greater than 7%.]. .Iadd.substantially zero .Iaddend.and a dye absorption value at 100° C. of no less 30%.
 23. The process of claim 22 wherein the nylon is nylon
 66. 24. The process of claim 22 wherein said finish contains, in addition to one or more stain blockers, one or more fluorochemicals.
 25. The process of claim 24 wherein the stain blocker(s) and fluorochemical are present in amounts sufficient to provide fiber coated with from 0.20 to 0.35% by weight of the stain blocker and from 450 to 650 ppm of fluorine, based on the weight of nylon.
 6. The process of claim 22 wherein said stain blockers are polymeric condensation products consisting essentially of repeating units of the formula ##STR10## where R is the same or different in each unit and is hydrogen or a radical selected from the group consisting of --SO₃ X, ##STR11## where X is hydrogen or a cation, wherein at least 40% of said repeating units contain an --SO₃ X radical and at least 40% of the repeating units contain the ##STR12## linkage.
 27. The process of claim 26 wherein said condensation products are mixed condensation products of phenol sulfonic acid with dihydroxy diphenolsulfone and formaldehyde.
 28. The process of claim 22 wherein said stain blockers are mixed condensation products of naphthalene monosulfonic acids with dihydroxy diphenylsulfones and formaldehyde. 